1. Field of the Invention
The present invention relates to a pattern antenna to be used for a wireless communication device. The present invention relates particularly to a pattern antenna for a wireless communication equipment which uses more than two frequencies.
2. Description of the Prior Art
It is conventional to use a wireless communication equipment which deals with more than two frequency bands. Systems used for such a wireless communication equipment include Frequency Division Multiple Access (FDMA) method utilizing Frequency Division Duplex (FDD) method in which separate frequency bandwidths are used for transmission and reception; and Time Division Multiple Access (TDMA) method and Code Division Multiple Access (CDMA) method that utilize the FDD method and Time Division Duplex (TDD) method in which time is separated by transmission and reception.
In wireless communication equipment, and in portable wireless communication devices in particular, in order to miniaturize the devices, it is required to miniaturize an antenna to be put into a casing of the wireless communication equipment. In order to miniaturize the antenna, inverted-F-shaped antennas are widely utilized. However, since the frequency bandwidth of the inverted-F-shaped antennas is several percentages in the bandwidth to center frequency ratio, and additionally, due to miniaturization, the frequency bandwidth of the antennas becomes narrow. As a result, as mentioned above, in wireless communication equipment utilizing systems which use more than two wireless frequency bands, the antennas cannot cover a wide frequency bandwidth which contains more than two necessary wireless frequency bands.
As a conventional technique to solve the above-mentioned problem, Japanese Patent Application Laid-Open No. 2000-68736 proposes a multi-frequency antenna consisting of an inverted-F type antenna, wherein a radiation conductor board which is in parallel with a grounding conductor board and to which electrical energy is fed through a coaxial cable has a plurality of unit radiation conductor boards of different length mounted thereon. As another conventional technique, Japanese Patent Application Laid-Open No. 2002-185238 proposes a built-in antenna device corresponding to dual band constituting of a plurality of planar radiation conductors of different length which are in parallel with a planar ground and to which electrical energy is fed by way of a feeding pin.
However, these conventional methods described in Japanese Patent Application Laid-Open Nos. 2000-68736 and 2002-185238, first of all, require a specific amount of space between the radiation conductor board and the ground surface and thus limit miniaturization and thinning of the antennas. In addition, in an aspect of production, a metal mold is necessary for cutting out of a conductor board. Therefore, whenever it is necessary to change the layout of components surrounding the antenna and/or a casing covering the antenna, it is necessary to change the shape of an antenna element, thus requiring a metal mold to be newly made or changed. Also, in order to support the radiation conductor board, it is necessary to insert a spacer between the ground board and the radiation conductor board or to bond a radiation conductor board to the inside of a non-electroconductive casing. Furthermore, in order to feed electrical energy to the radiation conductor board, a feeding pin is necessary to connect the radiation conductor board to the feeding point in an appropriate manner, and thereby it is a trouble and takes time to assemble these components.